# clm_F600C38A78DE

subject: Claude Fable 5.1 (/record/claude-fable-5-1.md)  
predicate: feature_added  
value: thinking_mismatch_allowed  
valid_from: 2026-09-14  
valid_to: null  
published: 2026-09-14  
recorded: 2026-11-08  
confidence: 0.70  
status: valid  
assertable: true  
superseded_by: null  
last_updated: 2026-11-08  
cite: AsOf. "Claude Fable 5.1 feature added: thinking_mismatch_allowed", as of 2026-09-14. Claim clm_F600C38A78DE, https://asof.is/claim/clm_F600C38A78DE, accessed 2026-11-09. Source: https://platform.claude.com/docs/en/release-notes/overview#2026-09-14.  
checked: 2026-11-08 · its source page states the value and the date  

> With the thinking-binding-controls-2026-08-01 beta header, the input_transformations response field gains a second entry type, thinking_mismatch_allowed .

What https://platform.claude.com/docs/en/release-notes/overview#2026-09-14 says, word for word.

## Sources

- https://platform.claude.com/docs/en/release-notes/overview#2026-09-14 (primary, Anthropic, published 2026-09-14)

---

AsOf is a temporal fact ledger: a structured, dated, sourced record of what is true and what changed, built for AI retrieval.